Method of lowering the cloud point of fatty acid esters

ABSTRACT

The present invention provides a robust and efficient process for reducing the cloud point of biodiesel fuel in which clathrates are formed from saturated fatty acid components as solvent is evaporated from a mixture of urea, methanol and fatty acid esters. The process speed can be fast, and is governed by the speed with which urea can be brought into clathrate forming contact with the fatty acid esters in the first instance, and then by the speed that solvent can be evaporated. Advantageously, substantially all of the solvent can be evaporated as pure solvent, which enhances process efficiencies and reduces cost. Additionally, substantially all of the urea can be used to form clathrates, further maximizing process efficiency.

RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.13/464,731, filed May 4, 2012, which is a continuation of InternationalPatent Application No. PCT/US2010/055464, filed Nov. 4, 2010, whichclaims priority to U.S. Provisional Patent Application No. 61/258,434,filed Nov. 5, 2009, all of which are hereby incorporated herein byreference in their entireties.

BACKGROUND OF THE DISCLOSURE

The present invention generally relates to fatty acid esters, and moreparticularly to a method for lowering cloud point of the fatty acidesters. A multitude of energy crises have been caused by disruption offossil fuel supplies, coupled with significantly increased demand forfossil fuels by industrialized nations. In the past few decades, thesecrises have encouraged the development of alternative fuels.Additionally, since there are finite reserves of crude oil from whichpetroleum-based fuels are derived, there has also been a trend towarddeveloping renewable fuels, such as biodiesel, which is derived fromrenewable sources.

Soy methyl ester (SME) or methyl soyate, the chemical description ofwhich is provided below, is a common organic acid ester precursor forproducing biodiesel. Organic acids, as the name indicates, are organiccompounds with acid-like properties. One common group of organic acidsare carboxylic acids, which have a “—COOH tail.” Esters constitute aclass of organic acid compounds where at least one —OH member isreplaced by an alkoxy group (—O—C_(n)H_(2n+1)). In the case of methylacetate ester, for example, a methoxy group (—O—CH₃), which is thesimplest form of an alkoxy, has replaced the —OH group in acetic acidCH₃COOH. This results in CH₃COOCH₃, or methyl acetate ester. Thischemical reaction is commonly termed esterification. Diagram 1, foundbelow, shows the chemical bond structures for these compounds.

Fatty acids consist mainly of carbon chains and hydrogen atoms. Thesechains can be short with a small number of carbon atoms, e.g., butyricacid (CH₃CH₂CH₂COOH), or long with large number of carbon atoms, e.g.,oleic acid CH₃(CH₂)₇CH═CH(CH₂)₇COOH. Fatty acids may include single anddouble bonds between carbon atoms. A saturated fatty acid has themaximum number of hydrogen atoms covalently bound to each carbon atom inthe chain of carbon atoms, i.e., a saturated fatty acid has no doublebonds. An unsaturated fatty acid has at least one double bond betweentwo carbon atoms. Diagram 2, found below, shows an example of saturatedand unsaturated fatty acids.

SME is produced by the transesterification of soybean oil with methanolin the presence of a catalyst. Transesterification results in a class oforganic reactions where one ester is transformed into another ester byinterchanging at least one alkoxy. The catalyst is often an acid orbase. For example, methanol is added to NaOH and added to soybean oil toseparate fatty acid esters from glycerin. In this example, the mixtureof NaOH, methanol, and soybean oil is often heated to accelerate theesterification step.

SME profile by percent and by molecular weight is given in Table 1,below.

TABLE 1 Typical SME profile Fatty Molecular Melting Percent of AcidCarbon Weight Point SME by Name Design Formula and Structure (g/mole) (°C.) Weight methyl palmitate C16:0

270.5   30.5 10.3 methyl stearate C18:0

298.5   39.1  4.7 methyl oleate C18:1

296.5 −19.8 22.5 methyl linoleate C18:2

294.5 −34.9 54.1 methyl linoleate C18:3 CH₃(CH₂CH═CH)₃(CH₂)₇CO₂CH₃ 292.5−57.0  8.3

Biodiesel produced by typical methods suffers from a crystallizationphenomenon when temperatures decrease. Although this crystallizationphenomenon is not limited to biodiesel, the temperature at whichbiodiesel begins to crystallize is substantially higher thanpetroleum-based diesel fuel. The crystallized constituents can clog fuelfilters in vehicles using biodiesel and thereby cut off the fuel supplyto the engine. The temperature at which solids begin to precipitate,thus producing a cloudy mixture, is referred to as cloud point (C.P.).Saturated fatty acid ester constituents crystallize at a highertemperature than unsaturated fatty acid esters. To lower the temperatureat which crystallization occurs and thereby lower the C.P. of the fuel,several techniques can be used, examples of which include blending withpetroleum-based diesel, introducing additives, and winterization.Winterization refers to crystallization and removal of saturated fattyacids, e.g., C16:0 and C18:0, and in some cases mono-unsaturated fattyacids, e.g., C18:1, that cause the biodiesel product to crystallize atan undesirably high temperature. The crystallization process istypically performed by cooling, and the removal process is typicallyperformed by filtration of the crystallized particles of the saturatedand in some cases mono-unsaturated fatty acids which leaves a mixturehaving a greater amount of polyunsaturated fatty acids compounds withlower C.P., thereby lowering the C.P. of the biodiesel so produced.

The winterization process has gained more interest in recent years.Winterization by itself produces low yields, i.e., a substantial portionof the starting material is lost during the filtration process.Therefore, use of compounds which improve the winterization process,typically referred to as “improvers,” is essential. One process whichincludes the addition of improvers is referred to as fractionation,which uses the crystallization properties of esterified fatty acids toseparate a mixture into low and high C.P. liquid fractions. Duringfractionation, these improvers create inclusion compounds/complexes. Theprocess of creating an inclusion compound involves a host constituent,namely, the fatty acid molecule, which has a series of cavities orlanding sites for attachment by a second chemical constituent, commonlyreferred to as the guest, which is an improver compound. The compoundresulting from the combination of the host and the guest is called an“inclusion compound.” The forces that hold the host and the guestconstituents together are van der Waals type forces. That is, covalentbonds do not typically form between the guest and the host. Clathratesare one type of inclusion compound in which the spaces in the hostconstituent are enclosed on all sides, causing a “trapping effect.”

A common improver compound is urea. Urea selectively forms clathrateswith fatty acid molecules. Initially, urea forms clathrates with longerstraight chain saturated fatty acid molecules, e.g., C18:0. As thenumber of longer chain saturated fatty molecules decline, urea thenforms inclusion compounds with shorter straight chain saturated fattyacids molecules, e.g., C16:0, and then with mono-unsaturated fatty acidmolecules that are nonlinear, e.g., C18:1. The reason for thisselectivity is thought to be the ease of clathration observed withlonger linear chain saturated fatty acids due perhaps to these moleucespossessing a larger number of landing sites for the urea molecule.

There are three different types of fractionation: dry fractionation,detergent fractionation, and solvent fractionation. Solventfractionation has received a substantial amount of interest in recentyears. The key to efficient fractionation is to thoroughly mix theimprovers, e.g., urea, with the fatty acids. Solvent is used as acarrier for the improver. That is, the improver is dissolved in thesolvent and the solvent-improver combination is added to the fatty acidto make a homogenous mixture.

Addition of solvent-improver to the fatty acid esters alone, however,does not promote formation of clathrates. For example, if urea isdissolved in methanol and the urea-methanol mixture is added to amixture of fatty acid esters to form a homogenous mixture, ureamolecules preferentially stay dissolved in methanol rather than formingclathrates with the fatty acid esters. In order to initiate the desiredclathration, a change in conditions must occur. In the prior art, inorder to begin the clathration, the homogenous mixture is cooled. As thehomogenous mixture is cooled, urea molecules begin to form clathratesbased on the selectivity described above. The clathrates crystallize andcan be separated by filtration, centrifugation, etc. As the homogenousmixture is formed the temperature is often elevated. This is due toheating in the transesterification phase in order to accelerate theesterification step, and since the homogenous mixture is often formeddirectly after the transesterification phase. The desired C.P. isdirectly proportional to how much the homogenous mixture is cooled. Forultralow C.P.s, the target cooling temperature is very low. Thus, due toa thermodynamic equilibrium, clathration formation slows unless thetemperature is further reduced. In order to form additional clathrates,the temperature must be further reduced.

However, clathration by cooling has several disadvantages. First,cooling the homogenous mixture is costly and in some cases not possible.For example, in many developing countries, the requirement to cool thehomogenous mixture is prohibitively expensive due, for example, to highambient temperature under some conditions. Second, cooling takes asubstantial amount of time. Large batches of fatty acid esters havecorrespondingly large thermal masses. Therefore, an undesirably longtime may be required to reach the target cooling temperature. Even ifthe homogenous mixture is allowed to naturally cool to room temperature,and thereby eliminate the need for active cooling, a substantial amountof time may be required due to the thermal mass. Also, relying onnaturally cooling to ambient temperatures may result in inconsistentoutput quality because the target cooling temperature may vary and thetarget temperature plays a key major role in the final product's C.P.Third, in cooling based processes involving typical target temperatures,some urea almost invariably stays dissolved in the solvent instead offorming clathrates. To quantify how much urea is used, urea utilizationis defined as a ratio of urea that forms clathrates to the total amounturea supplied in the process. In the cooling process, urea utilizationis always inherently below 100%. Fourth, the cooling process requireseventual separation of methanol from the unsaturated-rich fatty acidesters. This is required for commercial biodiesel because of industrystandards set for the final product which limit the amount of methanolin biodiesel, e.g., to 0.2% by volume.

What is needed is a robust, fast and efficient method of lowering thecloud point of Biodiesel that overcomes the drawbacks of the artdiscussed above.

SUMMARY

The present invention provides a robust and efficient process forreducing the cloud point of biodiesel fuel. In the inventive process,clathrates are formed from saturated fatty acid components as solvent isevaporated from a mixture of urea, methanol and fatty acid esters.

In one form thereof, the present invention provides a method of loweringthe cloud point of fatty acid esters. In this method, fatty acid estersare provided, to which a solvent and urea are added. Substantially allof the solvent is evaporated, thereby forming clathrates mixed withliquid having less saturated fatty acid esters than the fatty acidesters initially provided. Substantially all of the clathrates areseparated from the liquid; thereby, the liquid has a lower cloud pointthan the cloud point of the fatty acid esters initially provided.

Without wishing to be tied to any specific theory, it is thought that inthe process taught herein, the solvent merely provides a deliverymechanism to facilitate contact between the urea and fatty acid esters.After facilitating this initial contact, the solvent can be removedquickly. It is believed that clathrate formation continues as solvent isremoved from the mixture. That is, removing solvent effectivelyincreases the concentration of urea in the mixture, which in turnmaximizes the percentage of urea starting material that is used to formclathrates as compared to the cooling processes found in the prior art.This inventive process can remove substantially all of the solvent byevaporation (as pure solvent) early in the process and can also usesubstantially all of the urea to form clathrates. The resulting mixtureof clathrates and low cloud point biodiesel can be separated by any of avariety of separation mechanisms.

Advantageously, the inventive process can proceed very fast, withsubstantially all of the urea forming inclusion complexes withinminutes, as opposed to prior art processes which take hours and requirelarge amounts of energy for cooling. It is believed that thisadvantageously fast formation of clathrates results from the inventiveprocess being generally governed by equilibrium constraints rather thandynamic constraints. That is, process speed is largely governed in thefirst instance by the speed with which urea can be brought into“clathrate forming” contact with the fatty acid esters, and in thesecond instance the speed with which the solvent that facilitates the“clathrate forming” contact is removed. The faster these two processaspects are completed, the faster the overall process can be completed.

In this connection, it is generally preferable insofar as maximizingoverall process speed to conduct the evaporation in a vessel in whichthe ratio of surface area to volume is maximized, which facilitatesevaporation. On the other hand, the vessel selected should allow foradequate mixing of the urea, fatty acid esters and solvent to ensuresufficient clathrate forming contact opportunities between ureamolecules and fatty acid esters.

One advantage of the process of the present invention is its speed. Incontrast to prior art clathration by cooling processes, which require upto several hours for cooling, the inventive process can proceedessentially as quickly as clathrates can be formed and the solvent canthen be evaporated.

As a related advantage, the process of the present invention does notrequire cooling and the concomitant costs associated therewith. Indeed,the inventive process can be employed at the tail end of a biodieselmanufacturing process, in which the temperature of the biodiesel isalready elevated. Accordingly, the amount of energy needed to initiallyheat the solvent, urea and fatty acid esters, can thus be reduced.

Yet another advantage of the present invention is its efficient use ofmaterials. Unlike prior art processes, e.g., clathration by cooling, inwhich approximately one third of the urea may be unused (because itremains in solution), processes embodying these teachings can utilizesubstantially all of the urea for clathration, such that having toprocess an undesirable urea-solvent by-product is largely avoided. Inthe same vein, processes embodying these teachings typically evaporatepure solvent that can be reused without further process steps to removeunwanted constituents, e.g., urea. This facilitates a process having asimple and efficient solvent recycle stream and an economy of processsteps.

BRIEF DESCRIPTION OF DRAWINGS

The above-mentioned and other advantages of the present invention andthe manner of obtaining them, will become more apparent and theinvention itself will be better understood by reference to the followingdescription of the embodiments of the invention taken in conjunctionwith the accompanying drawings, wherein:

FIG. 1 is a schematic showing a transesterification process;

FIG. 2 is a schematic showing a first exemplary embodiment ofevaporative clathration in accordance with the current teachings;

FIG. 3 is a schematic showing a second exemplary embodiment ofevaporative clathration in accordance with the current teachings;

FIG. 4 is a schematic showing a third exemplary embodiment ofevaporative clathration in accordance with the current teachings; and

FIG. 5 is a schematic showing a forth exemplary embodiment ofevaporative clathration in accordance with the current teachings.

DETAILED DESCRIPTION

The embodiments described below are not intended to be exhaustive or tolimit the invention to the precise forms disclosed in the followingdetailed description. Rather, the embodiments are chosen and describedso that others skilled in the art may appreciate and understand theprinciples and practices of the present invention.

These teachings relate to lowering C.P. of fatty acid esters(hereinafter, “FAE”) by an evaporative process which produces inclusioncompounds mixed with refined liquid having a lower C.P. than thestarting FAE material. An example of FAE is SME. A solvent is used as acarrier for the urea; i.e., the urea is dissolved in the solvent. Asmentioned above, mixing urea/solvent with the FAE to generate a mixturein addition to changing at least one condition of the mixture promotesclathration. According to these teachings, evaporation of the solvent inwhich urea is dissolved is one change in the condition of the mixturethat promotes formation of clathrates. As the solvent is allowed toevaporate, the urea begins to shift from a state in which it isdissolved in the solvent to a state in which it is part of an inclusioncompound, or clathrate, with the FAE. In one embodiment, the clathratesare suspended solids in the FAE/urea/solvent mixture. The amount ofsolvent chosen is sufficient to dissolve the urea. The choice of howmuch urea should be added to the FAE is based on the desired C.P.depression. That is, according to the present teachings, lower C.P.values are achieved by adding more urea/solvent to the FAE, followed byevaporating the solvent.

Operation of diesel engines using renewable energy sources includingtriglycerides-derived fuels is known, as is the challenge of overcomingnegative properties of these triglycerides-derived fuels, e.g., thegelling of bioderived diesel (biodiesel) at higher temperatures thanpetroleum derived fuels. The composition of typical un-winterizedbiodiesel from SME is as given in Table 2.

TABLE 2 Composition of SME based biodiesel Fatty Acid Ester % by WeightMethyl Palmitate (C 16:0) ¹ 10.3 Methyl Sterate (C18:0) 4.7 MethylOleate (C18:1) 22.5 Methyl Linoleate (C 18:2) 54.1 Methyl Linolenate(C18:3) 8.3 ¹ The parenthetical reference (Cnn:n) indicates the numberof carbon atoms of the molecule on the left side of the colon followedby the number of carbon - carbon double bonds in the molecule on theright hand side of the colon.

Referring to FIG. 1, transesterification of a starting material isshown. Transesterification reactants comprise a fatty acid source, e.g.,soy oil, an alcohol, and a catalyst. Methanol is typically chosen as thereactant for SME transesterification, resulting in formation of themethyl ester from triglycerides. A hydroxide catalyst is typically usedto accelerate the transesterification, although the reaction alsoresponds to acid catalysis. Generally, mineral acids or mineral basesare selected as transesterification catalysts.

Typically, the transesterification of fatty acids from soy oil isconsidered “commercially complete” after a reaction time of from one tothree hours at reaction conditions. Total time of reactants in thereaction vessel may exceed these times if it is necessary to heatreactants to reaction temperature in situ. In commercial settings,completion of the transesterification reaction occurs when continuationof the transesterification cannot economically be sustained. Commercialcompletion may be influenced by many factors some related to theequipment involved. Examples of these factors include capitalcost/depreciation status, operating expense, size, geometry, separationequipment available, raw material cost, labor cost, or even the time ofday as it relates to an operator's shift change.

The range of fat sources is not limited. Commercial fat sourcesgenerally include oilseeds, often locally produced, such as soybeans andcanola. The carbon content of fatty acids from such sources ranges from16 to 22 carbon atoms per fatty acid molecule.

In one embodiment, transesterification of raw materials of fats is mostcommonly accomplished by supplying fats and alcohol in a molar ratio of1 mole fat (triglycerides) to 3 moles alcohol. Although the process isoperable outside this ratio, unreacted raw materials may result. Thereaction is observed to be nearly stoichiometric although it may beadvantageous to add excess alcohol to the esterification step as will bediscussed below. One percent catalyst by weight of fat is sufficient tofacilitate the reaction at a commercially acceptable rate. Insufficientcatalyst results in a slowed reaction; excess catalyst is not observedto significantly increase the reaction rate and may require additionalseparation effort at the completion of the reaction.

An example of the transesterification process is shown in FIG. 1. Sodiumhydroxide (NaOH) is mixed with methanol, creating methoxide in methanol.The mixture produces heat. Fatty acids (in this case soy oil) are addedto the methoxide mixture. The transesterification reaction generatesglycerin and methyl esters. Following a period of quiescence, theglycerin phase will separate from the methyl esters at the completion ofthe transesterification, forming a liquid phase of methyl ester on topof a liquid phase of glycerin. The phases may then be separated by,e.g., decanting the methyl esters. Other phase separation methods suchas a centrifugation may be used to accelerate and enhance the separationof glycerin from the methyl ester. The one exemplary technique for theabove-described transesterification process is illustrated by thefollowing example.

Transesterification of Soy Oil to Produce Un-Winterized SME Example:

Transesterification of soy oil with methanol in a vessel was completedwith 6 molar parts methanol to 2 molar parts refined soy oil. NaOH as acatalyst at the rate of 1% by weight of soy oil was included. The liquidcomponents were heated to 65° C. The condition was maintained for onehour with continuous mixing. The resulting two phases (upperlayer—soybean methyl esters, methanol, impurities; bottomlayer—glycerol, residual catalyst, impurities) were separated bydecantation, using a 1000 ml separatory funnel. Analysis of the methylester phase disclosed the composition by weight in Table 3a.

TABLE 3a Soy Oil Methyl Ester Fatty Acid Methyl Ester % by Weight MethylPalmitate (C 16:0) ¹ 10.9 Methyl Stearate (C18:0) 4.1 Methyl Oleate(C18:1) 25.9 Methyl Linoleate (C 18:2) 53.0 Methyl Linolenate (C 18:3)6.1 Others traces Total Saturates 15.0 C.P. (° C.) 3

For purpose of comparison, compositions of other vegetable oils arelisted in Table 3b, while compositions of the fats of some land andmarine animals are listed in Table 3c.

TABLE 3b* Fatty Acid Composition of Some Vegetable Oils (%) Oil C10:0C12:0 C14:0 C16:0 C18:0 C18:1 C18:2 C18:3 Cocoa butter 26 3.5 37 2.5Coconut 7 48 17 8 3 6 2 Corn 11 3 27 57 Cottonseed 0.8 25 2 18 53 0.1Olive 1 15 2.6 67 13 1 Palm 1 46 5 39 9 0.4 Palm kernel 3.6 50 16 8 2 151 Peanut 10 3 52 29 Rapeseed 3 1 25 17 8.5 Safflower 6 2 14 74 0.4Soybean 11 3.5 22 54 8 Sunflower 7 4 17 71 0.2

TABLE 3c* Fatty Acid Composition of Some Vegetable Oils (%) OilC4:0-12:0 C14:0 C16:0 C18:0 C18:1 C18:2 C18:3 C20:5 C22:6 Beef tallow 326 22 42 2 0.2 Butter 12 10.8 26 10.3 28 2 1 Chicken 0.9 22 10 41 20 2Lard 1.3 24 15.5 46 9 0.3 Mackerel 6 16 3 15 2 1 5 9 *Source: BaileyIndustrial Oil and Fat Products, 5^(th) edition, 1996, Vol. 1, EdibleOil and Fat Products: General Applications, Y. H. Hui, editor WileyInterscience, John Wiley and Sons, Inc.

A challenge posed by conventional biodiesel is its poor cold flowproperties. The total content of saturates is a typical conventionalbiodiesel about 15% (wt/wt) for SME, see Table 3a, and causes the C.P.to be about 0° C. and pour point to be about −2° C. to −4° C. Thislimits the use of SME at low temperatures. Various efforts have beenmade to reduce or depress the C.P. of SME. A popular method for removalof saturated components is winterizing or cold filtering. Variousstudies have been conducted; however, these methods have very low yieldsfor any significant reduction in the C.P.

These teachings disclose a C.P. reduction by a controlled removal of thesaturated, and in some cases, mono-unsaturated fractions by a processinvolving evaporative clathration with continued filtration ofclathrates rich in saturated and mono-unsaturated components. Theprocess parameters of greater significance are: 1) FAE/urea/solvent(weight/weight/volume ratio), and 2) the amount of solvent thatevaporates. The rate of evaporation appears to play an insignificantrole in the formation of urea clathrates as long as the mixture ofurea/FAE/alcohol is adequately mixed.

Referring to FIG. 2, one possible process for separating saturated andunsaturated fatty acid esters in accordance with the invention is shown.FAE, e.g., SME obtained from the transesterification process or fromother sources and used as a starting material, is introduced intoreactor 100. Reactor 100 can be in the form of a vessel or a conduit.The FAE starting material may already be at an elevated temperature,depending on whether the FAE is taken directly from thetransesterification process where it is formed. To start thefractionation process, an amount of urea dissolved in a solvent, e.g.,methanol is added to the FAE in reactor 100. A sufficient amount ofsolvent is used to dissolve the urea.

In one embodiment, once the volume of the FAE that is to be processedhas been added to reactor 100, a corresponding amount of urea andsolvent are also added to reactor 100. The ratio of FAE to ureadetermines the amount of clathration and subsequently the C.P.depression. As explained above, as the urea/solvent mixture is added tothe FAE and the solvent is allowed to evaporate, urea begins toselectively clathrate with the FAE. For effective clathration, themixture of urea/solvent and the FAE is continuously stirred or agitated.As will be described in greater detail below, solvent evaporation can beaccomplished by several methods. Whatever method is used to evaporatethe solvent, the starting material FAE should not reach its boilingcondition. Depending on different starting material the FAE boils atdifferent temperatures and pressures. In one embodiment the mixture ofFAE/urea/and solvent is heated to about 60° C. to about 70° C. atatmospheric pressure. The clathration selectivity is such that ureapreferentially begins to clathrate with C18:0, then with C16:0, and thenwith C18:1. If, however, there is sufficient urea present, clathrationcontinues with C18:2, and then with C18:3. Solvent is evaporated byheating the FAE/urea/solvent mixture or by applying a vacuum to themixture. Substantially all of the solvent is allowed to evaporate andsubstantially all of the urea is used to form clathrates. The compoundsthat form clathrates precipitate as solid particles that are suspendedin the mixture.

FAE flows through pipe 102 and through valve 104 into reactor 100. Flowmeter 103 and valve 104 are used to control the flow of FAE. In oneembodiment, flow meter 103 provides an electrical signal to a controllerwhich electrically controls valve 104. Flow of the FAE through pipe 102may be by gravity or a pump (not shown).

Solvent vessel 122 and urea vessel 120 include solvent and urea,respectively. Flow meters 118 and 116 measure the flow of the urea andsolvent. Valves 111 and 112 control the flow of the solvent and urea outof vessels 120 and 122. In one embodiment, flow meters 116 and 118provide electrical signals to a controller, which in turn electricallycontrols valves 111 and 112. The flow of solvent and urea from vessels122 and 120 may be by gravity or pumps (not shown). In one embodiment, asingle vessel including a mixture of urea and solvent can replace thetwo vessels 122 and 120. In this embodiment, the mixture of urea andsolvent should be continually agitated to maintain a homogenous mixture.Preferably, the ratio of urea to solvent should be such that the ureacompletely dissolves in the solvent. After the urea and solvent arebrought together, they are thoroughly mixed by inline static mixer 114.In the single vessel embodiment inline mixer 114 may be avoided. Theurea/solvent mixture flows through pipe 108 and into reactor 100 whereit is mixed with FAE. As mentioned above, the flow of urea and solventare monitored by flow meters 118 and 116 and the valves 112 and 111 arecontrolled so that the correct mixture of urea and solvent is achieved.The correct mixture is one where the urea can completely dissolve in thesolvent.

The mixture of FAE/urea/solvent is agitated with mixer propeller 132which is attached to shaft 136 held in housing 134. In one embodimentthe FAE/urea/solvent mixture is heated by heating element 140. Themixture is heated to a temperature that causes evaporation of thesolvent. The evaporated solvent flows through pipe 106. In oneembodiment pipe 106 has sufficient length in a helical direction toallow condensation as a result of heat exchange with ambient air. Inanother embodiment, pipe 106 leads to condenser 110 where the evaporatedsolvent condenses to liquid. In another embodiment, pipe 106 is coupledto a vacuum unit (not shown) which produces a negative pressure in thespace above the liquid in reactor 100, thereby aiding evaporation of thesolvent. Alternatively, heater element 140 and the vacuum unit may beused together to further accelerate evaporation of the solvent. In anyof the above cases, the condensed solvent may be recovered andreintroduced to solvent vessel 122 so that the solvent can be reused inthe process.

As the solvent begins to evaporate, urea molecules begin to selectivelyform clathrates with FAE molecules. With substantially all of thesolvent evaporated, the clathrates are in the form of solids suspendedin FAE rich in unsaturated fatty acids (hereinafter “UFAE”). The UFAEflows through filter 124, valve 141, flow meter 143, and pipe 142.Filter 124 is used for separating clathrates in the form of suspendedsolids from the UFAE. This separation occurs only when valve 141 isopened. Filter 124 can be a continuous filter such that after the filterhas collected sufficient clathrates, a new filter replaces the spentfilter. An example of filter 124 is a liquid-solid separator rotary drumfilter such as a Steadfast Equipment disposable rotary drum filter. Inone embodiment, a measured reduction in flow of UFAE through flow meter143 can be used as an indication to change the filter. In anotherembodiment (not shown in FIG. 2) the filter can be inside reactor 100.In this embodiment, filter 124 can be a continuous or rotary filter madeup of a several filtering surfaces which collect the suspendedclathrates as mixer propeller 132 agitates the FAE/urea/solvent mixture.

The UFAE exits reactor 100 by the force of gravity or actively by usinga pump (not shown) or by applying a vacuum. In one embodiment, acontroller receives an electrical signal from flow meter valve 143 andthe controller electrically controls valve 141. Valve 141 is opened onlywhen substantially all of the solvent has been evaporated. In order todetermine how much of the solvent has been evaporated, one of severalmethods can be used. Examples of these methods are: 1) masschromatography, 2) mass balance, 3) batch measurement using statisticalprocess control, and 4) flash point testing using samples to determinean amount of solvent that remains in the UFAE by evaporating the solventfrom the sample and measuring the flash point of the evaporated solvent.

In other embodiments, different separation techniques known to thoseskilled in the art can be used to separate the clathrates form the UFAE.Examples of these techniques, performed alone or in combination, arevacuum filtration, centrifugation, and solvent extraction. With some ofthese techniques a separation medium is used in combination with thetechnique. Also, in all of these techniques the separation step occursafter the evaporation step is completed. In the vacuum filtration case,a negative pressure is applied to the liquid extract, i.e., the UFAE,downstream from the separation medium. Application of vacuum acceleratesthe passage of the liquid extract through the separation medium.Alternatively, a positive pressure may be applied by air pump (notshown) to the interior head portion of reactor 100 to promote thepassage of the liquid extract through the separation medium. Thispositive pressure will only be applied after the evaporation stage iscompleted to make sure no interference occurs with the evaporationprocess. In the centrifugation technique the liquid UFAE is separatedfrom the clathrates by centrifuging these two components at speeds inthe range of about 10,000 to about 14,000 rpm. The centrifugationprocess results in separation of the two components into liquids thatcan be separated by, e.g., decantation. In the solvent extractiontechnique, a filtration solvent such as hexane is used, in which ureadoes not dissolve. The solvent is applied to the UFAE to accelerate theextraction from the clathrates. A filtration solvent in which ureacannot dissolve should be used to avoid a reverse clathration process.The filtration solvent is added to the mixture of FAE and clathrates andthe combination is filtered using a separation medium. Addition of thefiltration solvent promotes passage of the UFAE through the separationmedium.

The liquid that exits reactor 100 through pipe 142 is UFAE, and issubstantially free of solvent and urea. The UFAE flows to residualsolvent removal station 144. Although the goal is to evaporate andremove all of the solvent, traces of the solvent may be present in theUFAE. Substantially all of the initial urea, however, forms clathratesand zero to only trace amount of urea is present in the UFAE. The lowC.P. output of the process shown in FIG. 2 cannot contain anysignificant amount of solvent (see ASTM D6751 which limits methanolcontent to 0.2% by volume). The residual solvent removal station 144removes residual solvent. The low C.P. output flows out of pipe 146,while any solvent is removed through pipe 147. The removed solvent canbe optionally processed and recycled into solvent vessel 122. In oneembodiment, any residual solvent is evaporated and removed from the mainUFAE. In another embodiment, the solvent is washed with hot acidifiedwater, e.g., 60° C. and pH 3-4.

The filtered clathrates flow through pipe 126 to urea separation station128. Different techniques may be used to break down the clathrates andseparate the urea from the saturated-rich FAE (hereinafter SFAE). In oneembodiment, the clathrates are heated from about 110 to about 120° C. inorder to melt the urea from the SFAE, followed by separating the meltedurea from the SFAE by, e.g., decantation. In another embodiment, theurea is washed from the SFAE by applying warm water, e.g., about 65° C.,followed by separation of the SFAE and the washed urea. In thisembodiment, urea is more soluble in water than in SFAE. Therefore, theurea separates from SFAE and forms a layer below the SFAE. The lowerlayer is removed and the urea is dried, and preferably ground beforebeing recycled into the urea vessel. In yet another embodiment, theclathrates are mixed with a solvent in which urea cannot dissolve, e.g.,hexane. Due to the insolubility of urea in the solvent, ureaprecipitates from the mixture of solvent and SFAE. The liquid layerabove the urea containing SFAE and solvent is separated from the urea.The SFAE is separated from the solvent by evaporation or washing thesolvent from the SFAE. In all of these embodiments, the separated SFAEis a byproduct that has many uses where it is desired to have a high gelpoint, e.g., candles.

The process shown in FIG. 2 can be modified so that urea/solvent isadded in an incremental fashion. This alternative embodiment can preventa clogging condition which is described as follows. If all of thenecessary urea/solvent is added at once to the volume of FAE in reactor100, as substantially all of the solvent evaporates, substantially allof the urea forms clathrates in the form of a large amount of suspended“slurry-like” solids. As valve 141 is opened to allow the UFAE to exitreactor 100, the suspended solids can quickly clog filter 124, resultingin a reduction or blockage of FAE flow through valve 141.

In order to overcome this clogging problem, the known volume ofurea/solvent can be added to the FAE in increments. First, the amount ofurea/solvent that is needed to achieve the desired C.P. is determined.Then, under the control of a controller, that amount of urea/solvent isdivided into many increments and added to reactor 100. Filter 124 inthis embodiment is a continuous internal filter, e.g., a liquid-solidseparator rotary drum filter such as a Steadfast Equipment disposablerotary drum filter. As mentioned above, the FAE/urea/solvent mixtureshould be continuously mixed and agitated. As urea/solvent isincrementally added to reactor 100, conditions should be such that thesolvent in which the urea is dissolved quickly evaporates uponintroduction into reactor 100 causing quick clathration. A small amountof clathrates are formed with each increment of urea/solvent added tothe FAE. Under these conditions, the continuous filter does not sufferfrom the same clogging issue. As the final increment of urea/solvent isadded and the subsequent clathrate is filtered, valve 141 opens and theUFAE flows out of reactor 100. In this embodiment, filter 124continuously filters the suspended clathrates while a scraper assemblyseparates the solids from the filter medium. The separated solids aretransferred to urea separation station 128 for urea recovery and reuse.

Another possible embodiment is shown in FIG. 3. In this embodiment,incremental amounts of urea/solvent are added in an inline, stepwisefashion to the FAE. Solvent vessel 200 and urea vessel 206 containsolvent and urea which are mixed by static inline mixer 210, and themixture flows through several pipes 204. The flow of the solvent and theurea is examined and controlled by monitoring flow meters 202 and 208and controlling valves 111 and 112. In one embodiment, flow meters 202and 208 provide electrical signals to a controller which electricallycontrols valves 111 and 112. Flow of the solvent and urea from vessels200 and 206 may be by gravity or by use of pumps, not shown. In oneembodiment, a single vessel containing a mixture of urea and solvent canreplace the two vessels 200 and 206. In this embodiment, the mixture ofurea and solvent must be continually agitated to ensure a well mixedcombination. Also, the ratio of urea to solvent must be such that theurea completely dissolves in the solvent. After the urea and solvent arebrought together, the two are thoroughly mixed by inline, i.e., static,mixer 210. In the single vessel embodiment inline mixer 210 may beavoided. The urea/solvent mixture flows through pipe 204 and enterconduit 214 through valves 212, wherein the urea/solvent is mixed withFAE. As mentioned above, the flow of urea and solvent are monitored byflow meters 208 and 202 and the valves 112 and 111 are controlled sothat the correct mixture of urea and solvent is achieved. The correctmixture is one where the urea can completely dissolve in the solvent.

Several valves 212 control introduction of urea/solvent into the flow ofFAE flowing through conduit 214. The condition of conduit 214 is suchthat addition of urea/solvent at any point along conduit 214 causesimmediate evaporation of the solvent through pipes 224. This can beaccomplished by either applying a vacuum to conduit 214 or by heatingconduit 214. The evaporated solvent flows through pipe 217 and condenser218 and is recovered into solvent vessel 200. The evaporation of thesolvent also causes immediate selective clathration of urea with FAE.The clathrates are collected on inline filters 216, such as a SteadfastEquipment disposable rotary drum filter which has an integrated scrapingaction which separates the clathrates from the filter medium. Theclathrates are then transferred through pipes 226 to urea recoverystation 220. In urea recovery station 220, the urea is separated fromSFAE by any of the methods described above, e.g., disassociation byheating and thereby melting the urea, washing with warm water, andapplying a solvent in which urea is not dissolvable. With all of theseseparation techniques the urea is recovered and reintroduced into theurea vessel 206. The SFAE is used as a byproduct that has many useswhere it is desired to have a high gel point, e.g., candles.

Referring now to FIG. 4, a diagrammatic representation of anotherembodiment of a batch evaporative urea fractionation process, suitablefor practicing some of the embodiments of the invention is disclosed.Briefly, a pre-mixing vessel 302 is fitted with a series of valves (301a-e) and each valve is in turn connected to a source of at least onecompound that can be pre-mixed, for example, methanol (MeOH), recycledMeOH, urea and recycled urea. Next, the pre-mixed materials formed viapre-mixing vessel 302 are fed via pipe 303 into a blending/storage tank306 which is outfitted with a mixing means 308. Tank 306 is connectedvia pipe 305 to a source of FAE 307. After mixing, some of the contentsof tank 306 are fed via pipe 309 into crystallization chamber 312 whichis outfitted with a mixing means 310. The headspace in chamber 312 isconnected to an exhaust pipe 313 which is in turn connected to vacuumsource 317. Vacuum source 317 is outfitted with at least two liquidoutput pipes. Pipe 316 carries MeOH removed by vacuum from tank 310 backto mixing vessel 302. A second pipe 318 connected to vacuum source 317carries condensates having a boiling point different from the boilingpoint of MeOH away from vacuum source 317. Pipe 318 may be plumbed to awaste receptacle or to a purification apparatus (not shown) forseparation and/or fractionalization or additional processing of thecontents of pipe 318.

Still referring to FIG. 4, after a holding time in vessel 312 intendedto increase the level of clathrates produced in the process, a portionof the liquid content of vessel 312 is fed into pipe 320. Pipe 320 isalso connected to a filtration device, for example, rotary vacuumfiltration device 322. Solids such as clathrates form on the surface offiltration device 322. Liquid substantially free of clathrates such ascold flow-esters (CFE) flow though filtration device 322 and aretransferred out of the system via pipe 324. Excess liquid and/or solidmaterial from the surface of filtration device 322 may be re-applied tothe surface of device 322 via re-circulation pipe 326. Materialincluding both solids collected from the surface of filtration device322 and liquids substantially free of CFE are fed by pipe 326 to a heatsource such as 332. Liquid formed after heating by heating device 332 istransferred via pipe 334 to holding tank 336 which is vented via pipe335. Vent pipe 335 may be connected to a filtration, condensation orseparation unit (not show). Liquids that collect in tank 336 aboveflotation pipe 337 are siphoned out of holding tank 336 via pipe 338.This material is comprised primarily of saturate rich esters (SRE). Thecontents of tank 338 collecting in tank 336 below flotation line 337 areremoved from tank 336 via pipe 340. The material in pipe 340, whichincludes urea inclusion compounds (UIC), is fed into extrusion device342. The extrudate recovered from extrusion device 342 is highlyenriched in urea and is transferred by pipe 344 to pre-mixing vessel302.

Referring now to FIG. 5, a diagrammatic representation of asemi-continuous system suitable for practicing some of the embodimentsof the invention is shown. Pre-mixing vessel 402 is fitted with a seriesof valves (401 a-e). Each valve is in turn connected to a source of atleast one compound that can be pre-mixed, for example, methanol (MeOH),re-cycled MeOH, urea and re-cycled urea before the pre-mixture is mixedwith (FAE). Next, the pre-mixed material is fed into a blending/storagecontainer 406 which is outfitted with a mixing means 408 and is alsoconnected to a source of FAE. After mixing various components,including, for example, urea, methanol and FAE, a portion of thecontents of container 406 is fed via pipe 409 (which is fitted to ornear the bottom of tank 406) to a second tank 410 which includes mixingdevice 412. The head space of tank 410 is connected to pipe 414 which isin turn connected to a vacuum source 418. Alternatively, tank 410 may beheated (device not shown). Material is drawn from tank 410 by vacuumsource 418 and is fed to condenser 417 via pipe 416. Methanol iscollected from condensation unit 417 and is fed via recycle pipe 420 tomixing vessel 402. Material from condensation unit 417 that has aboiling point different from methanol is removed from condensation unit417 via pipe 419. Pipe 419 may be connected to a waste receptacle or toanother recovery and/or separation device (not shown). Liquid from tank410 is fed via pipe 423 to a filtration device such as rotary vacuumfiltration device 421. Liquids that pass through filtration device 421are collected via pipe 428. These liquids are substantially comprised ofcold-flow esters (CFE). Solid material that collects on the surface offiltration device 421 is enriched in urea inclusion compounds (UIC),including clathrates. This material is collected for additionalprocessing including, for example, the dissociation of urea inclusioncompounds to liberate urea from clathrates.

Still referring to FIG. 5, a tank 432 including filtered UIC collectedfrom, for example, the surface of rotary filtration device 421 is heatedto a temperature sufficient to dissociate the urea rich clathrates byheating device 436, which is connected to tank 432 via pipe 434. Meltedmaterial is fed via pipe 438 connecting heating device 436 to a settlingtank 440. Settling tank 440 is outfitted with head space vent pipe 442which may be connected to an additional condenser or separation device(not shown). Liquids in settling tank 440 above flotation line 443 arefed into pipe 445. This liquid is comprised substantially ofsaturate-rich esters (SRE) 446. Liquid collected in settling tank 440below flotation line 443 is removed from tank 440 via pipe 468. Pipe 468is in turn connected to a urea recovery device such as tray dryer 470.Vapor from tray dryer 470 is vented via pipe 472 while dried urea fromtray dryer 440 is collected via evacuation outlet 474 and may beintroduced into pre-mixing vessel 402.

These teachings provide numerous advantages over known prior art, forexample, prior art processes in which clathration is promoted by coolingthe mixture of FAE/urea/solvent. For example, substantially all of theurea is used in the clathration process. Since urea forms clathrateswith SFAE, the remaining UFAE is substantially free of urea and need notbe further processed to remove the urea. This means that smaller amountsof urea can be used for each batch of FAE as, for example, compared toclathration by cooling. Another advantage is that substantially all ofthe solvent is evaporated during the clathration process. Therefore,minimal processing is required to remove any traces of solvent that isleft in the UFAE. Additionally, little or no solvent is wasted using thesolvent recovery steps, described above. Also, evaporation ofsubstantially all of the solvent makes it possible for substantially allof the urea to clathrate with SFAE. Yet another advantage is that nocooling is required once urea/solvent have been added to the FAE topromote clathration. Still another advantage is that since theclathration process according to these teachings is closely controlled,the yield of the low gel point output is higher than, for example,clathration by cooling.

Exemplary techniques are illustrated by the following examples. Asummary of these examples is found in Table 4. In Table 4, FAEconstituents are listed for each example. Additionally, resulting C.P.,% by weight of starting FAE and the proportions of FAE to urea tosolvent is listed for each example.

EXAMPLE 1

50 grams of Soy Methyl Esters and 25 g of urea were added to 125 ml ofmethanol. The mixture was heated to ˜55° C., with constant stirring in around bottom flask. After all components were dissolved, the flask wasconnected to a rotary evaporator and the methanol was evaporatedapplying ˜20 in Hg of vacuum and a water bath at 60° C. 50 ml of hexanewere added to the residual contents of the flask and the contents of theflask were shaken for 2-3 minutes and then transferred into a Buchnerfunnel. The hexane extract was recovered by vacuum filtration,transferred into a round bottom flask and connected to a rotaryevaporator to flash off the hexane and thus recover the unsaturated-richsoy methyl esters. The yield was 69.1% of the initial SME mass. The FAEprofile of the material before and after treatment is shown in Table 4.

TABLE 4 Original SME Fractionated SME Fatty acid methyl esterComposition composition Methyl palmitate (C16:0) 10.5% 4.3% MethylStearate (C18:0) 5.7% 1.4% Methyl Oleate (C18:1) 25.8% 24.9% MethylLinoleate (C18:2) 49.7% 60.8% Methyl Linolenate (C18:3) 8.3% 8.6% Others(>C20) Traces 0 Total saturated fatty acids 16.2% 5.7% The cloud pointof the fractionated SME was −18° C.

EXAMPLE 2

20 grams of Soy Methyl Esters and 18 g of urea were added to 80 ml ofmethanol. The mixture was heated to ˜65° C., with constant stirring in around bottom flask. After all components were dissolved, the flask wasconnected to a rotary evaporator and the methanol was evaporatedapplying ˜20 in Hg of vacuum and a water bath at 60° C. 50 ml of hexanewere added to the residual contents of the flask and the contents of theflask were shaken for 2-3 minutes and then transferred into a Buchnerfunnel. The hexane extract was recovered by vacuum filtration,transferred into a round bottom flask and connected to a rotaryevaporator to flash off the hexane and thus recover the unsaturate-richsoy methyl esters. The yield was 63.3% of the initial SME mass. The FAEprofile of the material before and after treatment is shown in Table 5.

TABLE 5 Original SME Fractionated SME Fatty acid methyl esterComposition composition Methyl palmitate (C16:0) 10.5% ? Methyl Stearate(C18:0) 5.7% ? Methyl Oleate (C18:1) 25.8% ? Methyl Linoleate (C18:2)49.7% ? Methyl Linolenate (C18:3) 8.3% ? Others (>C20) Traces ? Totalsaturated fatty acids 16.2% ? The cloud point of the fractionated SMEwas −40.2° C.

EXAMPLE 3

20 grams of Soy Methyl Esters and 2 g of urea were added to 30 ml ofmethanol. The mixture was heated to ˜40° C., with constant stirring in around bottom flask. After all components were dissolved, the flask wasconnected to a rotary evaporator and the methanol was evaporatedapplying ˜20 in Hg of vacuum and a water bath at 60° C. 50 ml of hexanewere added to the residual contents of the flask and the contents of theflask were shaken for 2-3 minutes and then transferred into a Buchnerfunnel. The hexane extract was recovered by vacuum filtration,transferred into a round bottom flask and connected to a rotaryevaporator to flash off the hexane and thus recover the unsaturated-richsoy methyl esters. The yield was 92.1% of the initial SME mass. The FAEprofile of the material before and after treatment is shown in Table 6.

TABLE 6 Original SME Fractionated SME Fatty acid methyl esterComposition composition Methyl palmitate (C16:0) 10.5% 8.9% MethylStearate (C18:0) 5.7% 4.8% Methyl Oleate (C18:1) 25.8% 24.1% MethylLinoleate (C18:2) 49.7% 54.9% Methyl Linolenate (C18:3) 8.3% 7.3% Others(>C20) Traces Traces Total saturated fatty acids 16.2% 13.7% The cloudpoint of the fractionated SME was −4.5° C.

EXAMPLE 4

20 grams of Soy Methyl Esters and 4 g of urea were added to 30 ml ofmethanol. The mixture was heated to ˜60° C., with constant stifling in around bottom flask. After all components were dissolved, the flask wasconnected to a rotary evaporator and the methanol was evaporatedapplying ˜20 in Hg of vacuum and a water bath at 60° C. 50 ml of hexanewere added to the residual contents of the flask and the contents of theflask were shaken for 2-3 minutes and then transferred into a Buchnerfunnel. The hexane extract was recovered by vacuum filtration,transferred into a round bottom flask and connected to a rotaryevaporator to flash off the hexane and thus recover the unsaturated-richsoy methyl esters. The yield was 84.5% of the initial SME mass. The FAEprofile of the material before and after treatment is shown in Table 7.

TABLE 7 Original SME Fractionated SME Fatty acid methyl esterComposition composition Methyl palmitate (C16:0) 10.5% 7.6% MethylStearate (C18:0) 5.7% 4.0% Methyl Oleate (C18:1) 25.8% 24.1% MethylLinoleate (C18:2) 49.7% 57.0% Methyl Linolenate (C18:3) 8.3% 7.3% Others(>C20) Traces Traces Total saturated fatty acids 16.2% 11.6% The cloudpoint of the fractionated SME was −6.9° C.

EXAMPLE 5

20 grams of Soy Methyl Esters and 8 g of urea were added to 45 ml ofmethanol. The mixture was heated to ˜60° C., with constant stifling in around bottom flask. After all components were dissolved, the flask wasconnected to a rotary evaporator and the methanol was evaporatedapplying ˜20 in Hg of vacuum and a water bath at 60° C. 50 ml of hexanewere added to the residual contents of the flask and the contents of theflask were shaken for 2-3 minutes and then transferred into a Buchnerfunnel. The hexane extract was recovered by vacuum filtration,transferred into a round bottom flask and connected to a rotaryevaporator to flash off the hexane and thus recover the unsaturated-richsoy methyl esters. The yield was 84.7% of the initial SME mass. The FAEprofile of the material before and after treatment is shown in Table 8.

TABLE 8 Original SME Fractionated SME Fatty acid methyl esterComposition composition Methyl palmitate (C16:0) 10.5% 5.8% MethylStearate (C18:0) 5.7% 1.5% Methyl Oleate (C18:1) 25.8% 25.5% MethylLinoleate (C18:2) 49.7% 58.7% Methyl Linolenate (C18:3) 8.3% 8.5% Others(>C20) Traces Traces Total saturated fatty acids 16.2% 7.4% The cloudpoint of the fractionated SME was −12.7° C.

EXAMPLE 6

First step: 50 grams of Used Cooking Oil (UCO) Methyl Esters (seecomposition below) and 20 g of urea were added to 125 ml of methanol.The mixture was heated to ˜55° C., with constant stirring in a roundbottom flask. After all components were dissolved, the flask wasconnected to a rotary evaporator and the methanol was evaporatedapplying ˜20 in Hg of vacuum and a water bath at 60° C. The unsaturatedUCO methyl esters were recovered by vacuum filtration. The yield for thefirst step was 68.1%

Second step: 20 g of the fractionated methyl esters from the first stepwere used for a second fractionation by adding 18 g of urea and 80 ml ofmethanol. The same procedure as for the first step was followed toperform a second fractionation. The yield for the second stepfractionation was 38.6% of the initial UCO methyl esters masses. The FAEprofile of the material before and after treatment is shown in Table 9.

TABLE 9 Original UCO First Step - Second Step- Fatty acid methyl esterComposition composition composition C14:0 1.2% 1.4% 0.7% Methylpalmitate (C16:0) 22.5% 17.1% 5.6% Methyl Stearate (C18:0) 10.7% 7.2%0.7% Methyl Oleate (C18:1) 46.8% 52.0% 63.3% Methyl Linoleate (C18:2)16.7% 19.2% 25.8% Methyl Linolenate (C18:3) 1.2% 1.1% 1.7% C20:0 0.1%1.3 1.2% Others (>C20) 0.7% 0.8 1.0% Total saturated fatty acids 35.3%27.7% 9.1%

EXAMPLE 7

First step: 50 grams of Palm Oil Methyl Esters (PME; see compositionbelow) and 35 g of urea were added to 250 ml of methanol. The mixturewas heated to ˜55 C, with constant stirring in a round bottom flask.After all components were dissolved, the mixture was cooled down to 25°C. in a water bath; the urea clathrates formed were separated byfiltration. The methanol from the filtrate was removed by flashevaporation. A total of 30.5 g of PME was recovered in the filtrate (a61% yield).

Second step: The fractionated PME recovered from the first step wereused for a second fractionation by adding 25 g of urea and 250 ml ofmethanol. The same procedure as for the first step was followed toperform a second fractionation. The yield for the second stepfractionation was 40% of the initial PME methyl esters masses.

Third step: The fractionated PME recovered from the second step wereused for a third fractionation by adding 20 g of urea and 250 ml ofmethanol. The same procedure as for the first step was followed toperform a third fractionation. The yield for the third stepfractionation was 18% of the initial PME methyl esters masses. The FAEprofile of the material before and after treatment is shown in Table 10.

TABLE 10 Original First Second Third PME Step - Step- step - Fatty acidmethyl Composi- composi- composi- composi- ester tion tion tion tionMethyl palmitate 33.9% 34.0% 22.1% 2.6%  (C16:0) Methyl Stearate  6.5% 4.6%  1.3% 0% (C18:0) Methyl Oleate 45.9% 48.9% 58.7% 71.6%   (C18:1)Methyl Linoleate 13.7% 12.5% 17.9% 25.8%   (C18:2) Methyl Linolenate  0%   0%   0% 0% (C18:3) C20:0   0%   0%   0% 0% Others (>C20)   0%  0%   0% 0% Total saturated 40.4% 27.7% 23.4% 2.6%  fatty acids

It is envisioned that experimental results correlating C.P. to startingmaterial using different starting material can be provided to amathematical analysis package, e.g., SAS, for the purpose of fitting acurve to the experimental results. Such a mathematical analysis packagecan perform a regression analysis and provide a formula relating C.P. tomolar or weight fraction of the constituents of a starting material.Such a formula will advantageously provide an analytical tool forpredicting C.P. of a particular mixture by knowing the species of afatty acid profile that make up the mixture. For example, by knowing themolar or weight fractions of C16:0, C18:0, C18:1, C18:2 and C18:3 of aparticular mixture, a corresponding C.P. can be calculated.

It is also envisioned that experimental results correlating a particularstarting material to the amount of urea can be provided to amathematical analysis package, e.g., SAS, for the purpose of fitting acurve to the experimental results. Such a mathematical analysis packagecan perform a regression analysis and provide a formula relating theamount of urea needed compared to the known starting material to achievea particular C.P.

While exemplary embodiments incorporating the principles of the presentinvention have been disclosed hereinabove, the present invention is notlimited to the disclosed embodiments. Instead, this application isintended to cover any variations, uses, or adaptations of the inventionusing its general principles. Further, this application is intended tocover such departures from the present disclosure as come within knownor customary practice in the art to which this invention pertains andwhich fall within the limits of the appended claims.

What is claimed is:
 1. A method of lowering the cloud point of fattyacid esters, comprising: (a) providing fatty acid esters; (b) addingsolvent to the fatty acid esters; (c) adding urea to the fatty acidesters; (d) mixing the fatty acid esters, solvent and urea; (e)evaporating the solvent, thereby forming a clathrate-liquid mixture,wherein substantially all of the urea added in step (c) is used to formclathrates; and (f) separating the clathrates from the liquid in themixture formed in step (e), thereby forming refined fatty acid estershaving a lower cloud point than that of the fatty acid esters providedin step (a).
 2. The method of claim 1, wherein the method takes placealong a conduit, wherein steps (a), (b) and (c) comprise adding thefatty acid esters, the solvent and the urea to the conduit,respectively.
 3. The method of claim 2, wherein the fatty acid estersare added to the conduit prior to the adding of the urea and solvent tothe conduit.
 4. The method of claim 3, wherein urea and solvent areadded to the conduit together through a common inlet.
 5. The method ofclaim 1, wherein step (e) is performed after steps (b)-(c).
 6. Themethod of claim 5, wherein step (f) comprises feeding theclathrate-liquid mixture to a filter.
 7. The method of claim 1, whereinsteps (b)-(f) are repeated multiple times.
 8. The method of claim 7,wherein steps (a)-(f) are performed in sequence.
 9. The method of claim7, wherein the cloud point of the refined fatty acid esters produced instep (f) is reduced each time steps (b)-(f) are repeated.
 10. The methodof claim 7, further comprising reusing in step (b) at least some of theevaporated solvent obtained from step (e).
 11. The method of claim 1,wherein step (e) comprises evaporating substantially all of the solvent.12. The method of claim 1, wherein step (f) comprises separatingsubstantially all of the clathrates from the liquid in the mixtureformed in step (e).
 13. The method of claim 1, further comprisingprocessing the clathrates obtained from step (f) by separating the ureafrom saturate enriched fatty acid esters.
 14. The method of claim 13,wherein the step of separating the urea from fatty acid esters that areenriched in saturated fatty acid esters comprises: washing theclathrates with heated water to form a first layer of fatty acid estersand a second layer of urea dissolved in the heated water; separating thesecond layer of the urea dissolved in the heated water; and drying theurea.
 15. The method of claim 13, further comprising: mixing theclathrates with a urea separation solvent in which urea does notsignificantly dissolve to form a first layer of fatty acid esters mixedwith the urea separation solvent and a second layer of urea; separatingthe second layer of the urea from the first layer; and drying the urea.16. The method of claim 15, wherein the urea separation solvent ishexane.
 17. The method of claim 13, wherein the separated urea is reusedin step (c).
 18. A method of lowering the cloud point of fatty acidesters, comprising: providing a mixture including urea, fatty acidesters and a volatile solvent which dissolves urea; drawing a vacuumthat removes the volatile solvent from the mixture and thereby increasesthe effective concentration of urea in the mixture; using substantiallyall of the urea in the mixture to form clathrates; and separating theclathrates and saturate rich esters from the liquid comprisedsubstantially of cold flow esters.
 19. The method of claim 18, whereinthe step of drawing a vacuum removes substantially all of the volatilesolvent.
 20. The method of claim 18, wherein the step of separatingclathrates comprises separating substantially all of the clathrates fromthe liquid.
 21. The method of any of claim 18, further comprisingprocessing the clathrates into separate components of urea and saturateenriched fatty acid esters.